﻿#define _CRT_SECURE_NO_WARNINGS 1
\
class Solution
{
public:
	vector<vector<int>> threeSum(vector<int>& nums)
	{
		vector<vector<int>> ret;
		// 1. 排序
		sort(nums.begin(), nums.end());
		// 2. 利⽤双指针解决问题
		int n = nums.size();
		for (int i = 0; i < n; ) // 固定数 a
		{
			if (nums[i] > 0) break; // ⼩优化
			int left = i + 1, right = n - 1, target = -nums[i];
			while (left < right)
			{
				int sum = nums[left] + nums[right];
				if (sum > target) right--;
				else if (sum < target) left++;
				else
				{
					ret.push_back({ nums[i], nums[left], nums[right] });
					left++, right--;
					// 去重操作 left 和 right
					while (left < right && nums[left] == nums[left - 1]) left++;
					while (left < right && nums[right] == nums[right + 1])
						right--;
				}
			}
			// 去重 i 
			i++;
			while (i < n && nums[i] == nums[i - 1]) i++;
		}
		return ret;
	}
};